Genital herpes, though not recognized as a disease until 1966, is currently an epidemic venereal disease. Genital warts, a disease characterized by hyperplastic squamous epithelial growth caused by human papilloma virus infection is one of the most common sexually transmitted diseases in the U.S. today. Interferon (IFN) seems to have an especially high potential for the treatment of herpes, genital warts and other similarly manifested viral disease states. "Drug delivery" remains the singularly most limiting factor to the effective treatment of herpes and condyloma with interferon. Liposomes recently have received much attention in the search for a more effective means of delivering intrinsically active drugs to their tissue targets, Recently we have demonstrated that topically applied liposomal IFN is active in vivo against herpesvirus and acts as an immunological agent. The goal of these studies is to extend the development of topical liposomal delivery systems to treat a variety of skin diseases with interferon. While we have demonstrated effective prototypes, it now seems important to optimize drug delivery to reach tissue concentrations needed for therapeutic effectiveness. It is our hypothesis, now supported by substantial data, that liposomal composition is a major factor influencing the topical delivery of interferon through the skin.